Bigger weight loss, bigger drop-out rates: what a 100,000-patient study found

The weight-loss drugs that helped patients shed the most kilograms were also the ones most likely to cause side effects severe enough to make people quit treatment altogether, according to a large new analysis published in The BMJ.

Researchers examined 262 clinical trials involving roughly 100,000 participants and 19 different medications, uncovering a clear trade-off: greater weight loss consistently came paired with a higher risk of side effects or treatment discontinuation. Tirzepatide, used in Mounjaro and Zepbound, and the still-unapproved CagriSema delivered the biggest weight-loss results among the drugs studied.

Despite these gains, none of the medication groups showed a clinically meaningful improvement in quality-of-life scores compared with patients making lifestyle changes alone. “Most agents do not improve quality of life meaningfully and few show cardiovascular benefits,” the study authors concluded.

The findings also flagged a hidden risk in the most powerful drugs: harmful loss of lean mass, tied to a higher risk of falls, bone fractures and early death. Experts including José M. Ordovás from Tufts University say the results reinforce that treating obesity successfully should be measured by overall health and daily function, not just the number on a scale.